The present invention relates generally to lamp covers, and is particularly concerned with a lamp cover for a fluorescent lamp. Such lamp covers are known which are transparent or translucent and are appropriate for covering the lamp upward or downward.
The basic problem of such lamp covers is that the light-directing design of the lamp cover must be such that no disturbing shadows occur to the extent that light-impervious objects lie in the ray path and a certain light-directing effect is desired. In addition, the surface on one side of the lamp cover features a certain structure at least on one side.
Some known lamp covers have grooves that run longitudinally to the lamp cover, parallel to one another and at a reciprocal distance from each other, and that form a triangular structure (prism structure) in cross-section (profile). A disadvantage of this known lamp cover with prism structure is that it may bring about striation on illuminated surfaces and that shadowing elements located in the ray path may lead to undesired visibility, i.e. such elements may be readily seen from the outside. To the extent that one wishes to avoid such shadow formations, it is known to opalesce such lamp covers. The disadvantage however is that it produces relatively high diffusion losses. The related disadvantage is that the lamp cover continues to appear bright even from relatively flat angles of view, which is undesirable in many applications.
It also contradicts the appropriate norm.
In addition, such opal material also diffuses back into the lamp, which leads to efficiency losses.